Solar box cookers and solar panel cookers normally do not need to be turned to follow the sun unless you are cooking beans or an especially large amount of food, or if you are cooking on a day where sunlight is not optimal. They may need to be turned once over a three- or four-hour cooking period. However, parabolic solar cookers require reorientation with the sun much more often. If tracking the sun is necessary, some of the ideas below will serve this purpose.

When designing tracking systems, it can useful to determine the annual movement of the sun for various locations. Besides annual range, this useful tool also gives real-time sun information for a specific location. Suncalc.org

The 2016 Edition of the Solar Electricity Handbook also offers a convenient visual tool to calculate the sun's position in virtually all cities around the globe. It can be found at: Solar Angle Calculator

Contents

News

Responsive Materials

Possible candidate for a low-tech solar tracker: This is an exploration of materials and their capacity to respond dynamically to environmental triggers. These bimaterial prototypes are able to respond to directly to light, heat and humidity by bending. Their opening and closing action has an array of possibilities for architecture as intelligent apertures and environmental control devices.

May 2018:Dr. Paul Sallis Senior Lecturer in Environmental Engineering reports: Concentrating Solar Power (CSP) devices such as solar cookers benefit greatly from accurate solar tracking, but this feature is usually too costly to apply commercially. This is because active solar trackers often employ optical sensors, microprocessors, and electromechanical devices to enable accurate alignment of the collector with the sun throughout the day. Simpler systems are possible whereby thermally responsive materials such as shape memory alloys (SMA) provide the mechanical force to drive the tracking movement, however, these materials are still costly and are not sustainable in many countries. Research at Newcastle University has shown that responsive materials such as hygromorphic composites (HC) can generate significant useful mechanical force that can be utilised in a passive actuator to achieve mechanical tracking of simple solar cookers or other CSP. These HC materials give predictable and consistent time-dependent responses which means they act as mechanical clocks and need no feedback control from sensors to achieve accurate solar tracking, the required rotation of 15 degrees per hour simply being achieved by an adjustable mechanical linkage to the rotation axis of the solar collector (e.g. solar cooker). There is considerable scope for this research to be developed further, with a partner from the solar cooking industry, into a low-cost high-performance solar cooker for conventional applications. However, it would also open up new opportunities to use such a device for household-level disinfection of drinking water (boiling). This is particularly relevant in low and middle-income countries where simple sustainable technologies are needed to deal with waterborne pathogens in untreated drinking water.

Mechanical tracking systems

Simply Solar provides explanation of their various tracking systems at
Scheffler tracking systems. The mechanical system incorporates a clockwork mechanism, and often uses recycled bicycle parts. It is run by a weight and controlled by a pendulum. Resetting the reflector back from the evening position to the morning position is done by hand. They also offer photovoltaic options as well.

Programmable tracking systems

Still in its infancy, programmable tracking systems are being developed with software to not only rotate the reflector to maintain maximum exposure to the sun, but also to control cooking time and desired temperatures. One example of an auto tracking and monitoring system is the SolarCue system. Another is the Raspberry Pi: Solrmatic, but there are a range of such programmable sun trackers.[1]

Photovoltaic tracking systems

A clever system has been developed by several designers, which uses two photovoltaic panels configured to maintain an even balance of power to a small electrical turntable motor. Typically, the required photovoltaic panels are fairly small and are placed side by side, but at slightly different angles to face the sun. As the sun moves across the sky, one panel will begin to receive less direct sunlight.

The resulting electrical imbalance causes the dominant panel to engage the motor. The turntable will rotate until both photovoltaic panels face the sun equally and the motor disengages. The simple system can be fairly lightweight for rotating a box or panel cooker. However, a larger parabolic solar cooker, which will benefit the most from a good tracking system, will require a stronger motor and larger panels to rotate the cooker.

Tracking for the HotPot solar cooker

Most are familiar with the HotPot, a fine quality cooker. It does an excellent job of representing a solar cooker as a desirable appliance. However, the original design was created for use in tropical or semi-tropical areas bounded by the Tropic of Cancer (23.5° N) and the Tropic of Capricorn (23.5° S). The reflectors have been oriented for a more overhead sun position, which limits the cooking time in temperate locations to a 2- to 4-hour window. The following article talks more about this issue. The author has been working on a tilting base mechanism to allow the reflectors to pick up early and late day sun. However, it may be a better idea to supplement the HotPot reflectors with a windshield shade tipped forward and wrapped behind the cooker to catch the early and late day sun, as the pot and glass enclosure are really not suited for non-level conditions. Details on this tracking design here.

Solrmatic

The Solrmatic is a programmable turntable system intended to provide more control over when and how often a solar cooker needs to be reoriented with the sun. It can work with many existing manufactured or homemade solar box cookers and solar panel cookers when they are placed on the turntable.

The Solrmatic features thermostats, time delay, timed cooking, and web monitoring, allowing you to cook almost everything you normally cook in a traditional oven. The Solrmatic has cooked leg of lamb, brisket, veggies, bread, cookies, bacon, and even dehydrated apples.

Documents

Audio and video

Wolfgang Scheffler explains the workings of two of his automatic tracking parabolic cooking systems and the design of his solar food dryer.

December 2014:

Responsive Materials

Possible candidate for a low-tech solar tracker: This is an exploration of materials and their capacity to respond dynamically to environmental triggers. These bimaterial prototypes are able to respond to directly to light, heat and humidity by bending. Their opening and closing action has an array of possibilities for architecture as intelligent apertures and environmental control devices.

May 2013:

Solar oven tracker wiring

A very clear short video of a simple photovoltaic tracking mechanism.

February 2013:

CATASSOL automatizado 1

Pleno Sol provides a short demonstration of the photovoltaic tracking system they have developed.

March 2011:

Solar Oven with Tracker .mpg

Box cooker rotated by PV panels sending power to 12-volt motor. As one PV panel begins to receive less light, it sends less power to the servo, which operates the motor until both panels are sending a balanced power stream.

December 2010:

Smart Solar Oven Platform Benchtop Test.wmv

December 2010:

Cooking a Yam 12-30-10.wmv

Programmable system tracks the sun and turns the reflector away when cooking is completed.